The direct integration of semiconductor devices with a variety of electroactive materials has made possible a new generation of microelectronic sensor devices. The most frequently used vehicle for this work has been the field-effect transistor (FET) in its various forms. Of these, the one most frequently adopted has been the insulated-gate FET. Typical devices are those disclosed in UK Pat. No. 1529743 and U.S. Pat. Nos. 4,411,741 and 4,437,969.
Hitherto, difficulty has been experienced with electrochemical sensing semiconductor devices due (a) to the inherent thermal sensitivity of FET structures, (b) non-linear response due to superposition of a chemically-derived signal on the intrinsic device transfer characteristics and (c) the unsuitability of existing devices for driving multiplexing circuitry where fast voltage transients may be present.
These problems have now been overcome with a novel integrated device structure.